Have you ever experienced "psychological blindness"?. 99% of vision is in the brain, not the eye. Have you ever looked so hard for something, that you did not see it, even though you were looking right at it? Sleep or nap is the cure.
Alot of "avant-garde" companies now have "nap-rooms" where "bleary-eyed" workers can close their eyes for 20 minutes. It has been found to actually increase productivity and accuracy, far outweighing the lost time for the nap.
Caffeine actually makes you more susceptible to "psychological blindness". A little caffeine may be good, too much may be bad.
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